Process of preparing molybdenum complexes, the complexes so-produced and lubricants containing same

ABSTRACT

Antioxidant additives for lubricating oil are prepared by combining an acidic molybdenum compound, a basic nitrogen compound complex and a sulfur source to form a sulfur- and molybdenum-containing composition.

FIELD OF THE INVENTION

This invention relates to new lubricating oil compositions. Morespecifically, it relates to new lubricating oil compositions containingantioxidant molybdenum compounds.

BACKGROUND OF THE INVENTION

Molybdenum disulfide has long been known as a desirable additive for usein lubricating oil compositions. However, one of its major detriments isits lack of oil solubility. Molybdenum disulfide is ordinarily finelyground and then dispersed in the lubricating oil composition to impartfriction modifying and antiwear properties. Finely ground molybdenumdisulfide is not an effective oxidation inhibitor in lubricating oils.

As an alternative to finely grinding the molybdenum disulfide, a numberof different approaches involving preparing salts of molybdenumcompounds have been tried. One type of compound which has been preparedis molybdenum dithiocarbamates. Representative compositions aredescribed in U.S. Pat. No. 3,419,589, which teaches molybdenum (VI)dioxide dialkyldithiocarbamates; 3,509,051, which teaches sulfurizedoxymolybdenum dithiocarbamates; and 4,098,705, which teaches sulfurcontaining molybdenum dihydrocarbyl dithiocarbamate compositions.

An alternative approach is to form dithiophosphates instead ofdithiocarbamates. Represenatative of this type of molybdenum compoundare the compositions described in U.S. Pat. No. 3,494,866, such asoxymolybdenum diisopropylphosphorodithioate.

U.S. Pat. No. 3,184,410 describes certain dithiomolybdenylacetylacetonates for use in lubricating oils.

Braithwaite and Greene in Wear, 46 (1978) 405-432 describe variousmolybdenum-containing compositions for use in motor oils.

U.S. Pat. No. 3,349,108 teaches a molybdenum trioxide complex withdiethylenetriamine for use as an additive for molten steel.

Russian Pat. No. 533,625 teaches lube oil additives prepared fromammonium molybdate and alkenylated polyamines.

Another way to incorporate molybdenum compounds in oil is to prepare acolloidal complex of molybdenum disulfide or oxysulfides dispersed usingknown dispersants. U.S. Pat. No. 3,223,625 described a procedure inwhich an acidic aqueous solution of certain molybdenum compounds isprepared and then extracted with a hydrocarbon ether dispersed with anoil soluble dispersant and then freed of the ether. U.S. Pat. No.3,281,355 teaches the preparation of a dispersion of molybdenumdisulfide by preparing a mixture of lubricating oil, dispersant, and amolybdenum compound in water or C₁₋₄ aliphatic alcohol, contacting thiswith a sulfide ion generator and then removing the solvent. Dispersantssaid to be effective in this procedure are petroleum sulfonates,phenates, alkylphenate sulfides, phosphosulfurized olefins andcombinations thereof.

SUMMARY OF THE INVENTION

It has been found that a lubricating oil additive can be prepared bycombining an acidic molybdenum compound, a basic nitrogen-containingcomposition, and a sulfur source, to form a molybdenum and sulfurcombining complex.

DETAILED DESCRIPTION OF THE INVENTION

Lubricating oil compositions containing the additive prepared asdisclosed herein are effective as either fluid and grease compositions(depending upon the specific additive or additives employed) forinhibiting oxidation, imparting antiwear and extreme pressureproperties, and/or modifying the friction properties of the oil whichmay, when used as a crank-case lubricant, lead to improved mileage.

The precise molecular formula of the molybdenum compositions of thisinvention is not known with certainty; however, they are believed to becompounds in which molybdenum, whose valences are satisfied with atomsof oxygen or sulfur is either complexed by or the salt of one or morenitrogen atoms of the basic nitrogen containing compositions used in thepreparation of these compositions.

The molybdenum compounds used to prepare the compositions of thisinvention are acidic molybdenum compounds. By acidic is meant that themolybdenum compounds will react with a basic nitrogen compound asmeasured by ASTM test D-664 or D-2896 titration procedure. Typicallythese molybdenum compounds are hexavalent and are represented by thefollowing compositions: molybdic acid, ammonium molybdate, sodiummolybdate, potassium molybdate and other alkaline metal molybdates andother molybdenum salts such as hydrogen salts, e.g. hydrogen sodiummolybdate, MoOCl₄, MoO₂ Br₂, Mo₂ O₃ Cl₆, molybdenum trioxide or similaracidic molybdenum compounds. Preferred acidic molybdenum compounds aremolybdic acid, ammonium molybdate, and alkali metal molybdates.Particularly preferred are molybdic acid and ammonium molybdate.

The basic nitrogen compound must have a basic nitrogen content asmeasured by ASTM D-664 or D-2896. It is preferably oil-soluble. Typicalof such compositions are succinimides, carboxylic acid amides,hydrocarbyl monoamines, hydrocarbon polyamines, Mannich bases,phosphonamides, thiophosphonamides, phosphoramides, dispersant viscosityindex improvers, and mixtures thereof. These basic nitrogen-containingcompounds are described below (keeping in mind the reservation that eachmust have at least one basic nitrogen). Any of the nitrogen-containingcompositions may be after-treated with e.g., boron, using procedureswell known in the art so long as the compositions continue to containbasic nitrogen. These after-treatments are particularly applicable tosuccinimides and Mannich base compositions.

The mono and polysuccinimides that can be used to prepare thelubricating oil additives described herein are disclosed in numerousreferences and are well known in the art. Certain fundamental types ofsuccinimides and the related materials encompassed by the term of art"succinimide" are taught in U.S. Pat. Nos. 3,219,666, 3,172,892, and3,272,746, the disclosures of which are hereby incorporated byreference. The term "succinimide" is understood in the art to includemany of the amide, imide, and amidine species which are also formed bythis reaction. The predominant product, however, is a succinimide andthis term has been generally accepted as meaning the product of areaction of an alkenyl subtituted succinic acid or anhydride with anitrogen containing compound. Preferred succinimides, because of theircommercial availability, are those succinimides prepared from ahydrocarbyl succinic anhydride, wherein the hydrocarbyl group containsfrom about 24 to about 350 carbon atoms, and an ethylene amine, saidethylene amines being especially characterized by ethylene diamine,diethylene triamine, triethylene tetraamine, and tetraethylenepentamine. Particularly preferred are those succinimides prepared frompolyisobutenyl succinic anhydride of 70 to 128 carbon atoms andtetraethylene pentaamine or triethylene tetraamine or mixtures thereof.

Also included within the term succinimide are the cooligomers of ahydrocarbyl succinic acid or anhydride and a poly secondary aminecontaining at least one tertiary amino nitrogen in addition to two ormore secondary amino groups. Ordinarily this composition has between1,500 and 50,000 average molecular weight. A typical compound would bethat prepared by reacting polyisobutenyl succinic anhydride and ethylenedipiperazine. Compositions of this type are disclosed in U.S. Ser. No.816,063 filed July 15, 1977 the disclosure of which is herebyincorporated by reference.

Carboxylic amide compositions are also suitable starting materials forpreparing the products of this invention. Typical of such compounds arethose disclosed in U.S. Pat. No. 3,405,064, the disclosure of which ishereby incorporated by reference. These compositions are ordinarilyprepared by reacting a carboxylic acid or anhydride or ester thereof,having at least 12 to about 350 aliphatic carbon atoms in the principalaliphatic chain and, if desired, having sufficient pendant aliphaticgroups to render the molecule oil soluble with an amine or a hydrocarbylpolyamine, such as an ethylene amine, to give a mono or polycarboxylicacid amide. Preferred are those amides prepared from (1) a carboxylicacid of the formula R² COOH, where R² is C₁₂₋₂₀ alkyl or a mixture ofthis acid with a polyisobutenyl carboxylic acid in which thepolyisobutenyl group contains from 72 to 128 carbon atoms and (2) anethylene amine, especially triethylene tetraamine or tetraethylenepentaamine or mixtures thereof.

Another class of compounds which are useful in this invention arehydrocarbyl monoamines and hydrocarbyl polyamines, preferably of thetype disclosed in U.S. Pat. No. 3,574,576, the disclosure of which ishereby incorporated by reference. The hydrocarbyl, which is preferablyalkyl, or olefinic having one or two sites of unsaturation, usuallycontains from 9 to 350, preferably from 20 to 200 carbon atoms.Particularly preferred hydrocarbyl polyamines are those which arederived, e.g., by reacting polyisobutenyl chloride and a polyalkylenepolyamine, such as an ethylene amine, e.g. ethylene diamine, diethylenetriamine, tetraethylene pentaamine, 2-aminoethylpiperazine,1,3-propylene diamine, 1,2-propylenediamine and the like.

Another class of compounds useful for supplying basic nitrogen are theMannich base compositions. These compositions are prepared from a phenolor C₉₋₂₀₀ alkylphenol, an aldehyde, such as formaldehyde or formaldehydeprecursor such as paraformaldehyde, and an amine compound. The amine maybe a mono or polyamine and typical compositions are prepared from analkylamine, such as methylamine or an ethylene amine, such as,diethylene triamine, or tetraethylene pentaamine. The phenolic materialmay be sulfurized and preferably is dodecylphenol or a C₈₀₋₁₀₀alkylphenol. Typical Mannich bases which can be used in this inventionare disclosed in U.S. Pat. No. 4,157,309, and U.S. Pat. Nos. 3,649,229,3,368,972 and 3,539,663, the disclosures of which are herebyincorporated by reference. The last application discloses Mannich basesprepared by reacting an alkylphenol having at least 50 carbon atoms,preferably 50 to 200 carbon atoms with formaldehyde and an alkylenepolyamine HN(ANH)_(n) H where A is a saturated divalent alkylhydrocarbon of 2 to 6 carbon atoms and n is 1-10 and where thecondensation product of said alkylene polyamine may be further reactedwith urea or thiourea. The utility of these Mannich bases as startingmaterials for preparing lubricating oil additives can often besignificantly improved by treating the Mannich base using conventionaltechniques to introduce boron into the composition.

Another class of composition useful for preparing the additives of thisinvention are the phosphoramides and phosphonamides such as thosedisclosed in U.S. Pat. Nos. 3,909,430 and 3,968,157 the disclosures ofwhich are hereby incorporated by reference. These compositions may beprepared by forming a phosphorus compound having at least one P-N bond.They can be prepared, for example, by reacting phosphorus oxychloridewith a hydrocarbyl diol in the presence of a monoamine or by reactingphosphorous oxychloride with a difunctional secondary amine and amono-functional amine. Thiophosphoramides can be prepared by reacting anunsaturated hydrocarbon compound containing from 2 to 450 or more carbonatoms, such as polyethylene, polyisobutylene, polypropylene, ethylene,1-hexene, 1,3-hexadiene, isobutylene, 4-methyl-1-pentene, and the like,with phosphorus pentasulfide and nitrogen-containing compound as definedabove, particularly an alkylamine, alkyldiamine, alkylpolyamine, or analkyleneamine, such as ethylene diamine, diethylenetriamine,triethylenetetraamine, tetraethylenepentaamine, and the like.

Another class of nitrogen-containing compositions useful in preparingthe molybdenum compositions of this invention includes the so-calleddispersant viscosity index improvers (VI improvers). These Vi improversare commonly prepared by functionalizing a hydrocarbon polymer,especially a polymer derived from ethylene and/or propylene, optionallycontaining additional units derived from one or more co-monomers such asalicyclic or aliphatic olefins or diolefins. The functionalization maybe carried out by a variety of processes which introduce a reactive siteor sites which usually has at least one oxygen atom on the polymer. Thepolymer then contacted with a nitrogen-containing source to introducenitrogen-containing functional groups on the polymer backbone. Commonlyused nitrogen sources include any basic nitrogen compound especiallythose nitrogen compounds and compositions described herein. Preferrednitrogen sources are alkylene amines, such as ethylene amines, alkylamines, and Mannich bases.

Preferred basic nitrogen compounds for use in this invention aresuccinimides, carboxylic acid amides, and Mannich bases.

Representative sulfur sources are sulfur, hydrogen sulfide, sulfurmonochloride, sulfur dichloride, phosphorus pentasulfide, R₂ S_(x) whereR is hydrocarbyl, preferably C₁₋₄₀ alkyl, and x is at least 2, inorganicsulfides and polysulfides, such as (NH₄)₂ S_(x), where x is at least 1,thioacetamide, thiourea, and mercaptans of the formula RSH where R is asdefined above. Also useful as sulfurizing agents are traditionalsulfur-containing antioxidants such as wax sulfides and polysulfides,sulfurized olefins, sulfurized carboxylic and esters and sulfurizedester-olefins, and sulfurized alkylphenols and the metal salts thereof.

The sulfurized fatty acid esters are prepared by reacting sulfur, sulfurmonochloride, and/or sulfur dichloride with an unsaturated fatty esterunder elevated temperatures. Typical esters include C₁ -C₂₀ alkyl estersof C₈ -C₂₄ unsaturated fatty acids, such as palmitoleic, oleic,ricinoleic, petroselinic, vaccenic, linoleic, linolenic, oleostearic,licanic, paranaric, tariric, gadoleic, arachidonic, cetoleic, etc.Particularly good results have been obtained with mixed unsaturatedfatty acid esters, such as are obtained from animal fats and vegetableoils, such as tall oil, linseed oil, olive oil, caster oil, peanut oil,rape oil, fish oil, sperm oil, and so forth.

Exemplary fatty esters include lauryl tallate, methyl oleate, ethyloleate, lauryl oleate, cetyl oleate, cetyl linoleate, laurylricinoleate, oleyl linoleate, oleyl stearate, and alkyl glycerides.

Cross-sulfurized ester olefins, such as a sulfurized mixture of C₁₀ -C₂₅olefins with fatty acid esters of C₁₀ -C₂₅ fatty afids and C₁ -C₂₅ alkylor alkenyl alcohols, wherein the fatty acid and/or the alcohol isunsaturated may also be used.

Sulfurized olefins are prepared by the reaction of the C₃ -C₆ olefin ora low-molecular-weight polyolefin derived therefrom with asulfur-containing compound such as sulfur, sulfur monochloride, and/orsulfur dichloride.

Also useful are the aromatic and alkyl sulfides, such as dibenzylsulfide, dixylyl sulfide, dicetyl sulfide, diparaffin wax sulfide andpolysulfide, cracked wax-olefin sulfides and so forth. They can beprepared by treating the starting material, e.g., olefinicallyunsaturated compounds, with sulfur, sulfur monochloride, and sulfurdichloride. Particularly preferred are the paraffin wax thiomersdescribed in U.S. Pat. No. 2,346,156.

Sulfurized alkyl phenols and the metal salts thereof includecompositions such as sulfurized dodecylphenol and the calcium saltsthereof. The alkyl group ordinarily contains from 9-300 carbon atoms.The metal salt may be preferably, a group I or group II salt, especiallysodium, calcium, magnesium, or barium.

Preferred sulfur sources are sulfur, hydrogen sulfide, phosphorouspentasulfide, R₂ S_(x) where R is hydrocarbyl, preferably C₁₋₁₀ alkyl,and x is at least 3, mercaptans wherein R is C₁₋₁₀ alkyl, inorganicsulfides and polysulfides, thioacetamide, and thiourea. Most preferredsulfur sources are sulfur, hydrogen sulfide, phosphorus pentasulfide,and inorganic sulfides and polysulfides.

A method for preparing compositions of this invention is to prepare asolution of the acidic molybdenum precursor with a basicnitrogen-containing compound with or without diluent. The diluent isused, if necessary, to provide a suitable viscosity for easy stirring.If desired, ammonium hydroxide may also be added to the reaction mixtureto provide a solution of ammonium molybdate. This reaction is carriedout at a temperature from the melting point of the mixture to refluxtemperature. It is ordinarily carried out at atmospheric pressurealthough higher or lower pressures may be used if desired. This reactionmixture is treated with a sulfur source as defined above and thereaction mixture at a suitable pressure and temperature for the sulfursource to react with the acidic molybdenum and basic nitrogen compounds.In some cases, removal of water from the reaction mixture may bedesirable prior to completion of reaction with the sulfur source.

In the reaction mixture, the ratio of molybdenum compound to basicnitrogen compound is not critical; however, as the amount of molybdenumwith respect to basic nitrogen increases, the filtration of the productbecomes more difficult. Since the molybdenum component probablyoligomerizes, it is advantageous to add as much molybdenum as can easilybe maintained in the composition. Usually, the reaction mixture willhave charged to it from 0.01 to 2.00 atoms of molybdenum per basicnitrogen atom. Preferably from 0.4 to 1.0, and most preferably from 0.4to 0.7, atoms of molybdenum per atom of basic nitrogen is added to thereaction mixture.

The sulfur source is usually charged to the reaction mixture in such aratio to provide 0.1 to 4.0 atoms of sulfur per atom of molybdenum.Preferably from 0.5 to 3.0 atoms of sulfur per atom of molybdenum isadded, and most preferably, 1.0 to 2.6 atoms of sulfur per atom ofmolybdenum.

The lubricating oil compositions containing the additives of thisinvention can be prepared by admixing, by conventional techniques, theappropriate amount of the molybdenum-containing composition with alubricating oil. The selection of the particular base oil depends on thecontemplated application of the lubricant and the presence of otheradditives. Generally, the amount of the molybdenum containing additivewill vary from 0.05 to 15% by weight and preferably from 0.2 to 10% byweight.

The lubricating oil which may be used in this invention includes a widevariety of hydrocarbon oils, such as naphthenic bases, paraffin basesand mixed base oils as well as synthetic oils such as esters and thelike. The lubricating oils may be used individually or in combinationand generally have a viscosity which ranges from 50 to 5,000 SUS andusually from 100 to 15,000 SUS at 38° C.

In many instances it may be advantageous to form concentrates of themolybdenum containing additive within a carrier liquid. Theseconcentrates provide a convenient method of handling and transportingthe additives before their subsequent dilution and use. Theconcentration of the molybdenum-containing additive within theconcentrate may vary from 0.25 to 90% by weight although it is preferredto maintain a concentration between 1 to and 50% by weight. The finalapplication of the lubricating oil compositions of this invention may bein marine cylinder lubricants as in crosshead diesel engines, crankcaselubricants as in automobiles and railroads, lubricants for heavymachinery such as steel mills and the like, or as greases for bearingsand the like. Whether the lubricant is fluid or a solid will ordinarilydepend on whether a thickening agent is present. Typical thickeningagents include polyurea acetates, lithium stearate and the like.

If desired, other additives may be included in the lubricating oilcompositions of this invention. These additives include antioxidants oroxidation inhibitors, dispersants, rust inhibitors, anticorrosion agentsand so forth. Also anti-foam agents stabilizers, anti-stain agents,tackiness agents, anti-chatter agents, dropping point improvers,anti-squawk agents, extreme pressure agents, odor control agents and thelike may be included.

Certain molybdenum products that can be prepared by the process ofinvention also find utility in making brake lining materials, inhigh-temperature structural materials, in iron and steel alloys, incladding materials, in electroplating solutions, as components forelectrical discharge machine electrodes, as fuel additives, in makingself-lubricating or wear-resistant structures, as mold release agents,in compositions for phosphatizing steel, in brazing fluxes, in nutrientmedia for microorganisms, in making electrosensitive recording material,in catalysts for refining coal, oil, shale, tar sands, and the like oras stabilizers or curing agents for natural rubber or polymers.

What is claimed is:
 1. A process for preparing a sulfurizedmolybdenum-containing composition which comprises (1) reacting an acidicmolybdenum compound and a basic nitrogen compound selected from thegroup consisting of a succinimide, carboxylic acid amide, Mannich base,phosphonamide, thiophosphonamide, phosphoramide, dispersant viscosityindex improvers, or mixtures thereof, to form a molybdenum complexwherein from 0.01 to 2 atoms of molybdenum are present per basicnitrogen atom; and (2) reacting said complex with a sulfur containingcompound, in an amount to provide 0.1 to 4.0 atoms of sulfur per atom ofmolybdenum, to form a sulfur- and molybdenum-containing composition. 2.The process of claim 1 wherein the sulfur source is sulfur, hydrogensulfide, phosphorus pentasulfide, R₂ S_(x) where R is hydrocarbyl, and xis at least 2, inorganic sulfides, inorganic polysulfides,thioacetamide, thiourea, mercaptan of the formula RSH where R ishydrocarbyl, or a sulfur-containing antioxidant.
 3. The process of claim2 wherein the sulfur source is sulfur, hydrogen sulfide, phosphoruspentasulfide, R₂ S_(x) where R is C₁₋₄₀ hydrocarbyl, and x is at least3, an inorganic sulfide, or inorganic polysulfide, thioacetamide,thiourea or RSH where R is C₁₋₄₀ alkyl, and the acidic molybdenumcompound is molybdic acid, ammonium molybdate, or an alkali metalmolybdate.
 4. The process of claim 3 wherein said sulfur source issulfur, hydrogen sulfide, RSH where R is C₁₋₁₀ alkyl, phosphoruspentasulfide, or (NH₄)₂ S_(x'), where x' is at least 1, said acidicmolybdenum compound is molybdic acid or ammonium molybdate, and saidbasic nitrogen compound is a succinimide, carboxylic acid amide, orMannich base.
 5. The process of claim 4 wherein said basic nitrogencompound is a C₂₄₋₃₅₀ hydrocarbyl suffinimide, carboxylic acid amide, ora Mannich base prepared from a C₉₋₂₀₀ alkylphenol, formaldehyde, and anamine.
 6. The process of claim 5 wherein said basic nitrogen compound isa polyisobutenyl succinimide prepared from polyisobutenyl succinicanhydride and tetraethylene pentaamine or triethylene tetraamine.
 7. Theprocess of claim 5 wherein said basic nitrogen compound is a carboxylicacid amide prepared from one or more carboxylic acids of the formula R²COOH, or a derivative thereof which upon reaction with an amine yields acarboxylic acid amide, wherein R² is C₁₂₋₃₅₀ alkyl or C₁₂₋₃₅₀ alkenyland a hydrocarbyl polyamine.
 8. The process of claim 7 wherein R² isC₁₂₋₂₀ alkyl or C₁₂₋₂₀ alkenyl and the hydrocarbyl polyamine istetraethylene pentaamine or triethylene tetraamine.
 9. The process ofclaim 6 wherein said basic nitrogen compound is a Mannich base preparedfrom dodecylphenol, formaldehyde, and methylamine.
 10. The process ofclaim 6 wherein said basic nitrogen compound is a Mannich base preparedfrom C₈₀₋₁₀₀ alkylphenol, formaldehyde and triethylene tetraamine,tetraethylene pentaamine, or mixtures thereof.
 11. The product preparedby the process of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or
 10. 12. Alubricating oil composition comprising an oil of lubricating viscosityand from 0.05 to 15% by weight of the product of claim
 11. 13. Aconcentrate comprising an oil of lubricating viscosity and from 0.25 to90% by weight of the product of claim 11.